An AC power converter converts power from an AC power source to an AC load. A DC power holding source is coupled to an input half-bridge switch, a common half-bridge switch and an output half-bridge switch. A controller is coupled to the input half-bridge switch, the common half-bridge switch, and an output half-bridge switch to generate at least two control signals at a common switching frequency, wherein the controller generates the at least two control signals with a phase difference there between chosen to cause a ripple frequency in both the input low pass filter and the output low pass filter to be double the common switching frequency. An input low pass filter can eliminate switching frequency energy from entering the AC power source. An output low pass filter can eliminate switching frequency energy from entering the AC load.

An AC power converter converts power from an AC power source to an AC load. A DC power holding source is coupled to an input half-bridge switch, a common half-bridge switch and an output half-bridge switch. A controller is coupled to the input half-bridge switch, the common half-bridge switch, and an output half-bridge switch to generate at least two control signals at a common switching frequency, wherein the controller generates the at least two control signals with a phase difference there between chosen to cause a ripple frequency in both the input low pass filter and the output low pass filter to be double the common switching frequency. An input low pass filter can eliminate switching frequency energy from entering the AC power source. An output low pass filter can eliminate switching frequency energy from entering the AC load.

The present disclosure relates to a method for controlling a converter, in particular power converter of a wind power installation. The converter has a plurality of, preferably parallel, converter modules. The method includes the following steps: driving a first converter module, such that the converter module generates a first electrical AC current in a first switch position, driving a second converter module, such that the converter module generates a second electrical AC current in a second switch position, superposing the first electrical AC current and the second electrical AC current to form a total current, detecting the total current of the converter, determining a virtual current depending on the first and second switch positions, and changing the first switch position of the first converter module and/or the second switch position of the second converter module depending on the total current and the virtual current.

A power converter that includes a rectifier rectifying a voltage supplied from a three-phase AC power supply, a voltage step-down circuit including a voltage step-down switching element, a reactor, a backflow prevention element, and a smoothing capacitor and stepping down a DC voltage supplied from the rectifier, and an inverter circuit converting the DC voltage smoothed by the smoothing capacitor into an AC voltage. The power converter includes an imbalance determining unit determining, based on states of the voltage step-down circuit and the smoothing capacitor, whether or not voltage imbalance has occurred in the three-phase AC power supply and a voltage step-down control unit performing switching of the voltage step-down switching element in a case where the imbalance determining unit determines that the voltage imbalance has occurred.

A power converter that includes a rectifier rectifying a voltage supplied from a three-phase AC power supply, a voltage step-down circuit including a voltage step-down switching element, a reactor, a backflow prevention element, and a smoothing capacitor and stepping down a DC voltage supplied from the rectifier, and an inverter circuit converting the DC voltage smoothed by the smoothing capacitor into an AC voltage. The power converter includes an imbalance determining unit determining, based on states of the voltage step-down circuit and the smoothing capacitor, whether or not voltage imbalance has occurred in the three-phase AC power supply and a voltage step-down control unit performing switching of the voltage step-down switching element in a case where the imbalance determining unit determines that the voltage imbalance has occurred.

A motor drive apparatus includes: a rectifier; an inverter; a DC link voltage detection unit; an input current detection unit configured to detect input current inputted to the rectifier; a DC link voltage comparison unit configured to compare a DC link voltage with a first voltage threshold value and with a second voltage threshold value; a current comparison unit configured to compare the input current with a current threshold value; and an abnormality detection unit configured, in a case that the DC link voltage is smaller than the first voltage threshold value or that the DC link voltage is greater than the second voltage threshold value, to determine that a first abnormality has occurred when the input current is smaller than the current threshold value and to determine that a second abnormality has occurred when the input current is equal to or greater than the current threshold value.

A power train is described herein comprising a load, a first power supply for providing power to the load, a DC-link capacitor connected to the load, a main converter configured to convert DC power to AC power for powering the load; and pre-charge circuitry. The pre-charge circuitry comprises pre-charge means configured to, during a first, pre-charge phase, prevent said power from being provided to said load but provide power to said DC-link capacitor to charge said DC-link capacitor, and, further configured to, during a second, post-charge phase, allow said power to be provided from said first power supply to said load. A method for providing power to the load is also described herein.

A direct-current bus power supply as a power supply device supplies power to a load capable of switching a state between a driving state in which driving is performed by receiving power supply and a standby state in which driving is stopped while receiving power supply. The power supply device includes: a diode bridge circuit and capacitors as a rectifier circuit that enables an alternating-current voltage to be rectified by respective rectification systems of full-wave rectification and voltage doubler rectification; and a switching unit that perform switching between the full-wave rectification and the voltage doubler rectification on the basis of a voltage value of the alternating-current voltage and the state of the load.

An arrangement for determining an operation parameter reference for controlling a generator side converter portion coupled to a generator is provided, including: at least one arithmetic element configured to derive at least one harmonic current error by subtracting a generator output current from at least one harmonic current reference; at least one harmonic current controller configured to determine at least one harmonic reference current deviation based on the harmonic current error; another arithmetic element configured to derive a fundamental current error by subtracting the generator output current from a sum of a fundamental current reference and the at least one harmonic current reference; still another arithmetic element configured to determine a modified fundamental current error as a sum of the fundamental current error and the harmonic reference current deviation; a fundamental current controller adapted to determine the operation parameter reference based on the modified fundamental current error.

A control device includes: a phase generation unit to generate a phase of a voltage command for the power converter; a voltage control unit to generate a voltage value of the voltage command; and a command unit to output the voltage command having the phase and the voltage value to the power converter. The voltage control unit includes: a voltage compensator unit to compute a compensation voltage value, based on a voltage deviation of a point-of-interconnection voltage from a reference voltage; a droop calculator unit to compute a first droop value in accordance with a magnitude of a point-of-interconnection current, when the AC power system is an isolated system, the isolated system being the AC power system not connected to a generator; and a calculation unit to calculate the voltage value of the voltage command, based on a difference between the compensation voltage value and the first droop value.